The invention relates to a process for producing wear-resistant surfaces on components made from an AlSi alloy. The invention also relates to a configuration for producing wear-resistant surfaces on components made from an AlSi alloy.
Hypoeutectic aluminum-silicon alloys, which are predominantly used for cylinder crankcases, are unsuitable for the tribological loads of the piston/piston ring/cylinder bearing surface system, because of an insufficient level of the wear-resistant silicon phase. Hypereutectic alloys, e.g. the alloy AlSi7Cu4Mg have a sufficient number of silicon crystallites. This hard, wear-resistant microstructure constituent is raised with respect to the matrix formed of an aluminum mixed crystal by chemical and/or mechanical processing stages and forms a required load-bearing surface component. However, drawbacks are the castability, which is low compared to the hypoeutectic and almost eutectic alloys, poor machinability and the high costs of this alloy.
One possible way of avoiding these drawbacks is to cast in sleeves or liners made from a wear-resistant material, such as for example gray cast iron and hypereutectic aluminum alloys. However, a problem in this case is the join between the sleeve and the surrounding casting, because the join is achieved merely by mechanical meshing or interlocking. When using a porous ceramic liner material, it is possible to infiltrate the liner material during the casting process and thus to obtain a material-to-material bond. This requires a slow filling of the casting mold and the use of high pressure, which considerably reduces the economic efficiency of the process.
Alternatively, hypoeutectic and almost eutectic alloys of electrodeposition coatings are applied directly onto the cylinder bearing surfaces. However, this is expensive and these coatings cannot sufficiently withstand tribochemical loads. A further alternative are thermally sprayed layers, which are likewise applied directly to the cylinder bearing surfaces. However, the adhesive strength of these layers is insufficient, since they are joined only by a micromechanical interlocking.
Therefore, it has already been proposed to carry out the surface modifications of remelting, alloying, dispersing and coating by using a laser, as is disclosed, for example, in Published, Non-Prosecuted German Patent Application No. DE 196 43 029 A1. In this case, it is necessary to sufficiently dissipate the energy which is introduced into the crankcase or the cylinder bearing surfaces by the laser beams. The dissipation of energy is necessary because an excessively high input of heat with high-energy laser beams may lead to undesirable changes to the microstructure in the crankcase. For this purpose, Published, Non-Prosecuted German Patent Application No. DE 196 43 029 A1 has already proposed that the component surface be cooled via cooling-water channels of the crankcase.
It is accordingly an object of the invention to provide a process and a configuration for producing a wear-resistant surface on a component which overcome the above-mentioned disadvantages of the heretofore-known processes and configurations of this general type and which allow components to be coated even with high-energy coating devices, such as high-performance lasers, without causing heat-related changes to the material of the component.
With the foregoing and other objects in view there is provided, in accordance with the invention, a process for producing a wear-resistant surface on a component, the process includes the steps of:
providing a component formed of an AlSi alloy;
forming a wear-resistant surface on the component by using a thermal spraying or a laser beam treatment; and
bringing at least one thermally conductive device into a thermally conductive contact with the component such that the at least one thermally conductive device touches the component during the step of forming the wear-resistant surface; and
actively cooling the at least one thermally conductive device.
In other words, a process for producing wear-resistant surfaces on components made from an AlSi alloy is provided, wherein the wear-resistant surfaces are applied by thermal spraying or a laser beam, wherein, during the production of the wear-resistant surface, at least one thermally conductive device is brought into a thermally conductive contact with the component, and wherein this thermally conductive device is actively cooled.
The above-defined process has the advantage that a good dissipation of heat in combination with an increased cooling capacity is available during the coating operation, so that in particular a laser alloying and a laser coating can be carried out without the risk of a heat-related change in the structure of the material of the crankcase. This allows to carry out a coating at even higher energies, so that, for example, a greater depth of penetration of the coating material into the material of the component, a better join or connection between the coating and the material of the component and/or a greater layer thickness are achieved.
To further improve properties of the coating that is applied, after the formation of the wear-resistant surface in the form of a thermally sprayed layer, this layer is additionally treated with a laser beam. In particular, the layer is remelted with a laser beam.
As explained, the wear-resistant surface may be applied through the use of a thermal spraying, in particular a flame spraying, a plasma spraying or a HV (high velocity) spraying, or through the use of a laser beam.
According to a preferred mode of the invention, a remelting, alloying, dispersing and/or coating is carried out through the use of a laser beam or by thermal spraying.
The component, whose surface is to be treated, is for example a crankcase of a reciprocating internal combustion engine. The coating is to be carried out on cylinder bearing surfaces of cylinders of the crankcase. In this case, according to a preferred mode of the invention, during the production of the wear-resistant surface, a water space or water chamber of the crankcase has a cooling medium, in particular gas, nitrogen or a cooling liquid, flowing through it.
According to another mode of the invention, the thermally conductive device or heat-conducting device includes at least one cooling plate with passages for a cooling medium. The at least one cooling plate is put against the crankcase on at least one side on which open ends of the cylinders are situated.
According to yet another mode of the invention, the thermally conductive device includes at least one cooling mandrel which is formed such that it corresponds to the cross section of the cylinder and which is brought into contact with the cylinder bearing surface. The at least one cooling mandrel follows a coating zone on the cylinder bearing surface in an axial direction of the cylinder and/or trails the coating zone.
According to a further mode of the invention, the thermally conductive device includes a cooling-medium tank, into which the crankcase is dipped during the production of the wear-resistant surface, in such a manner that a cooling-medium level in the cylinder remains below a coating zone as seen in the direction of the force of gravity. In this case, an immersion depth, i.e. a depth to which the crankcase is dipped into the cooling-medium tank, is controlled in such a manner that a constant given distance is maintained between the coating zone and the cooling-medium level.
According to yet a further mode of the invention, the active cooling of the thermally conductive device is carried out by using a gas, nitrogen and/or a cooling liquid.
According to an advantageous mode of the invention, a honing operation is performed subsequent to the coating process according to the invention, in order to smooth the coated surface.
With the objects of the invention in view there is also provided, a configuration for producing a wear-resistant surface on a component, including:
a thermally conductive device configured to be disposed in a thermally conductive contact with a component formed of an AlSi alloy; and
the thermally conductive device being configured to operate with a cooling medium.
In other words, a configuration for producing wear-resistant surfaces on components made from an AlSi alloy, in particular on cylinder bearing surfaces of cylinders of a crankcase of a reciprocating internal combustion engine, includes a thermally conductive device which is disposed in a thermally conductive contact with the component and includes a cooling medium.
This has the advantage of a good dissipation of heat with an increased cooling capacity during the coating operation, so that in particular a laser alloying and a laser coating can be carried out without the risk that the heat causes a change in the structure of the material of the crankcase. Consequently, it is possible to carry out a coating using even higher energy levels, so that, for example, an increased depth of penetration of the coating material into the material of the component, a better join between the coating and the material of the component and/or a higher layer thickness are achieved.
The cooling medium expediently includes a gas, nitrogen and/or a cooling liquid, which have a high coefficient of heat capacity to ensure a correspondingly high dissipation of heat.
According to a preferred embodiment of the invention, the thermally conductive device includes at least one cooling plate with passages through which the cooling medium flows, wherein a cooling plate is disposed on the crankcase on at least one side of the crankcase where the cylinders have their open ends.
According to another feature of the invention, the thermally conductive device includes an annular cooling plate that is shaped such that it rests on a circumferential edge of a corresponding cylinder bore and such that it is aligned with the cylinder bore, i.e. it is in line with the cylinder bore. Thus a good dissipation of heat is achieved at the circumference of the cylinder bore.
According to another preferred embodiment of the invention, the thermally conductive device includes at least one cooling mandrel which is formed such that it corresponds to the cross section of a cylinder bore. The at least one cooling mandrel has passages through which the cooling medium flows. The at least one cooling mandrel is, in the axial direction of the cylinder, disposed on at least one side of a coating zone, i.e. the at least one cooling mandrel is disposed on one side or on both sides of a coating zone, in such a manner that a thermally conductive contact is formed between the at least one cooling mandrel and the cylinder bearing surface.
In order to achieve a high cooling capacity in the vicinity of the cylinder bearing surface, the passages through which the cooling medium flows are helical passages so that the cooling medium flows in a helically encircling manner.
In order to collect excess coating material, a cooling mandrel which is disposed beneath the coating zone, as seen in the direction of the force of gravity, is configured to have a collection basin for excess coating material.
In order to collect excess coating material and to introduce it into the collection basin, a collection lug or protrusion is formed on a side of the periphery of the cooling mandrel that faces the coating zone.
In order to increase the cooling action of the cooling mandrel, the cooling mandrel is formed, on its periphery which faces the cylinder bearing surface, with cooling bristles which are in brushing contact with the cylinder bearing surface. The cooling bristles are expediently made from a thermally conductive material, in particular copper.
According to another embodiment of the invention, the thermally conductive device includes at least one cooling-medium tank, into which the component can be dipped in such a manner that a cooling-medium level is at a given distance from a coating zone.
With the objects of the invention in view there is also provided, in combination with a component formed of an AlSi alloy, a configuration for treating the component, including:
a thermally conductive device including a cooling medium; and
the thermally conductive device being in a thermally conductive contact with the component.
According to another feature of the invention, the component is a crankcase having a cylinder with a cylinder bearing surface, and the thermally conductive device is in a thermally conductive contact with the cylinder bearing surface.
According to yet another feature of the invention, the cooling medium is a gas or a cooling liquid.
According to a further feature of the invention, the crankcase has a side formed with a cylinder opening, the thermally conductive device has a cooling plate disposed on the side formed with the cylinder opening, and the cooling plate is formed with channels for the cooling medium to flow therethrough.
According to yet a further feature of the invention, the cylinder is formed with a cylinder bore having a circumferential edge, the thermally conductive device has an annular cooling plate disposed along the circumferential edge and aligned with the cylinder bore, and the at least one annular cooling plate is formed with channels for the cooling medium to flow therethrough.
According to another feature of the invention, the cylinder has a cross section and has a coating zone on the cylinder bearing surface, the thermally conductive device includes a cooling mandrel formed to correspond to the cross section of the cylinder, the cooling mandrel is disposed in the cylinder on at least one side of the coating zone such that the thermally conductive contact is formed between the cooling mandrel and the cylinder bearing surface, and the cooling mandrel is formed with passages for the cooling medium to flow therethrough.
According to yet another feature of the invention, the passages are helical passages.
According to a further feature of the invention, the cooling mandrel is disposed, with respect to a direction of gravity, beneath the coating zone, and the cooling mandrel has a collection basin for receiving excess coating material.
According to an additional feature of the invention, the cooling mandrel has a peripheral region with a side facing the coating zone, and the cooling mandrel has a collection lug disposed on the side of the peripheral region facing the coating zone.
According to another feature of the invention, the cooling mandrel has a peripheral region facing the cylinder bearing surface, and the cooling mandrel has cooling bristles disposed at the peripheral region, and the cooling bristles are in brushing contact with the cylinder bearing surface.
According to another feature of the invention, the component has a coating zone, the thermally conductive device includes a cooling-medium tank filled with the cooling medium up to a cooling medium level, and the component is dipped into the cooling medium such that a given distance between the cooling-medium level and the coating zone is maintained.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a process and a configuration for producing wear-resistant surfaces, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.